EP2521358A1 - Image Cross-talk Cancellation in Stereoscopic Video Display Devices - Google Patents
Image Cross-talk Cancellation in Stereoscopic Video Display Devices Download PDFInfo
- Publication number
- EP2521358A1 EP2521358A1 EP11164807A EP11164807A EP2521358A1 EP 2521358 A1 EP2521358 A1 EP 2521358A1 EP 11164807 A EP11164807 A EP 11164807A EP 11164807 A EP11164807 A EP 11164807A EP 2521358 A1 EP2521358 A1 EP 2521358A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- image
- echo
- energy
- brightness
- image frame
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000000034 method Methods 0.000 claims abstract description 39
- 238000012545 processing Methods 0.000 claims abstract description 6
- 230000009466 transformation Effects 0.000 claims description 12
- 238000004364 calculation method Methods 0.000 claims description 9
- 230000004048 modification Effects 0.000 claims description 9
- 238000012986 modification Methods 0.000 claims description 9
- 239000000872 buffer Substances 0.000 claims description 8
- 230000003247 decreasing effect Effects 0.000 claims description 4
- 230000001419 dependent effect Effects 0.000 claims description 4
- 238000012886 linear function Methods 0.000 claims description 4
- 230000001131 transforming effect Effects 0.000 claims 3
- 230000006870 function Effects 0.000 description 19
- 230000000694 effects Effects 0.000 description 15
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 13
- 238000012937 correction Methods 0.000 description 10
- 239000011521 glass Substances 0.000 description 9
- 238000013459 approach Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 7
- 230000004044 response Effects 0.000 description 5
- 230000006978 adaptation Effects 0.000 description 4
- 230000008447 perception Effects 0.000 description 4
- 210000004556 brain Anatomy 0.000 description 3
- 238000005282 brightening Methods 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000007781 pre-processing Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 230000035484 reaction time Effects 0.000 description 3
- 230000001360 synchronised effect Effects 0.000 description 3
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 230000008033 biological extinction Effects 0.000 description 2
- 230000003139 buffering effect Effects 0.000 description 2
- 239000003086 colorant Substances 0.000 description 2
- 230000005284 excitation Effects 0.000 description 2
- 239000004973 liquid crystal related substance Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 241001203771 Eudonia echo Species 0.000 description 1
- 230000003044 adaptive effect Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 238000004422 calculation algorithm Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 230000004438 eyesight Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000002688 persistence Effects 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000002123 temporal effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- 230000016776 visual perception Effects 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
- H04N13/30—Image reproducers
- H04N13/398—Synchronisation thereof; Control thereof
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
- H04N13/10—Processing, recording or transmission of stereoscopic or multi-view image signals
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
- H04N13/10—Processing, recording or transmission of stereoscopic or multi-view image signals
- H04N13/106—Processing image signals
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
- H04N13/30—Image reproducers
- H04N13/332—Displays for viewing with the aid of special glasses or head-mounted displays [HMD]
- H04N13/341—Displays for viewing with the aid of special glasses or head-mounted displays [HMD] using temporal multiplexing
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0209—Crosstalk reduction, i.e. to reduce direct or indirect influences of signals directed to a certain pixel of the displayed image on other pixels of said image, inclusive of influences affecting pixels in different frames or fields or sub-images which constitute a same image, e.g. left and right images of a stereoscopic display
Definitions
- the present Invention generally relates to display devices for reproducing stereoscopic video data, in particular to display devices employing a field-sequential method and including an image cross-talk cancellation capability for improving the quality of three-dimensional image reproduction.
- the 3D perception from the Human Visual System is based on the close side-by-side positioning of the eyes as shown in Fig. 1 .
- Each eye takes a view of the same area from a slightly different angle.
- These two separate images are sent to the brain for processing. When the two images arrive simultaneously in the back of the brain, they are united into one picture.
- the human mind combines the two images by matching up the similarities and adding the small differences to catch finally a three-dimensional stereo picture.
- stereovision the HVS sees an object as solid in three spatial dimensions (width, height and depth) and it is the additional perception of the depth dimension that makes stereovision so rich and special.
- a stereo picture will increase the impression of sharpness in the brain.
- 3D images are generated using two video cameras positioned side-by-side in a similar way than the human eyes.
- Other methods mainly based on complex software are also able to generate artificial stereo pictures by ray tracing (simulation of light propagation).
- these images will be referred to as left and right images. If right and left images stemming from a video source are displayed in a sequential and alternating manner as shown in Fig. 2 and if a synchronized shutter system in front of the eyes allows the right image to only enter the right eye and conversely, then a three-dimensional video reproduction can be observed.
- the shutter can be mounted in eyeglasses and is synchronized with a display in which two constituent pictures are presented in alternation instead of simultaneously.
- the glasses occlude either the left eye or the right eye in synchronism with the image displaying.
- a simple method to implement a stereoscopic display is based on the separation of sub-fields into left (L) and right (R) groups which are synchronized with the open and close stage of the LCD shutter glasses.
- An advantage of such a method is the compatibility of the flat panel display (FPD) between 2D and 3D modes. This compatibility is ensured through a simple change of the display mode (single or double frame rate).
- This method is often called “field-sequential" or "active-glass system” and enables to keep the full resolution of the display in 3D.
- polarizer systems i.e. a passive glass system
- each odd and even line is dedicated to another eye, thus reducing the displayed resolution in 3D by a factor two.
- polarizer filters are built on the front glass of the panel, thus reducing partly its brightness both in 2D as well as in 3D.
- this field-sequential method can introduce other discomfort such as the introduction of time parallax between the two images, or the possibility of "ghosting" or crosstalk between the images due to the time response of the display (e.g.
- LCDs liquid crystal displays
- Most glasses-shutter systems use LCDs which work with polarized light.
- glasses using LCDs can provide good switching speed and reasonable extinction of the alternative lenses.
- the electro-optical polarizing shutters available on the market today transmit less than 30% of the unpolarized input light (rather than 50% for perfect polarizers) and this reduces the image brightness tremendously.
- Some eyeglass shutters are connected by wires to the monitor, others are controlled by infrared or by radio communication and are wireless.
- Displaying stereo pictures on a flat panel display also requires the capability to display two different pictures per frame (i.e. doubling the frame rate) which is a new challenge for this technology.
- Figure 3 illustrates the response of each phosphor element to the same excitation in the case of a plasma display panel (PDP).
- the response time of the phosphor elements associated with the colors red and green is longer than that of the phosphor elements associated with the color blue, which is almost equal to the primary excitation (UV light caused by the gas or plasma discharge inside the PDP cells).
- UV light caused by the gas or plasma discharge inside the PDP cells.
- the phosphor elements activated for the left image are still luminous while the right image is displayed or, in other words, after the opening of the right glass. Consequently, there will be a so-called “ghost image” (also denoted as “echo”) visible in the right image but stemming from the left image, and on a subsequent left image an echo image stemming from the right image can be observed.
- This cross-talk effect is illustrated in Figure 4 , which shows how subfields behave in such a configuration.
- the stereoscopic system as described above requires the left image to be seen only by the left eye, and the right image to be seen only by the right eye.
- the right eye will receive some fraction of the luminance of the left image and conversely.
- the phosphor lag will prevent a proper stereoscopic effect since the right eye receives both right and left information.
- the echo (or crosstalk) image is usually perceived as a kind of doubled image (remaining parts of left image are superimposed to the right one and vice versa) and lead to a lack of sharpness or even to a temporal loss of the depth perception in some particular cases (e.g. in case of images with strong contrast).
- the mentioned ghost images and the related image crosstalk are a problem that has to be considered when using a display technology with not-instant reaction time (such as PDPs and LCDs in field-sequential mode) for stereoscopic image reproduction.
- image cross-talk may also appear when using other video reproduction devices such as video projectors or the like, and the problems mentioned above are not limited to PDPs.
- a method for processing video data comprising a sequence of successive image frames comprises: receiving an image frame from a video data source; calculating a first echo image based on the image frame; providing a second echo image based on a further image frame preceding the image frame; calculating an echo compensated image frame by subtracting the difference of the echo images from the image frame.
- One option to avoid the image cross-talk as discussed in the introduction is to subtract an estimated echo image (or "ghost image"), which is obtained from one (e.g. left) image, from the subsequent (e.g. right) image.
- an estimated echo image or "ghost image”
- a sufficient compensation of the echo image i.e. a sufficient cross-talk cancellation
- Such a method is illustrated in Fig. 5 .
- the flow diagram of Fig. 5 illustrates one exemplary method of pre-processing stereoscopic video data in order to avoid visible echo images in the images actually displayed.
- an echo image E i is estimated from one frame F i ' of a video signal to be displayed.
- a frame represents the brightness values of the (red, blue and green) pixels composing one single left or right image.
- This echo estimation may be performed separately for each color channel, whereby in applications using PDPs for 3D image presentation the blue channel may remain uncompensated. Further a look-up table (LUT) of pre-calculated data may be used for such estimation.
- the estimated echo image E i is stored in a frame buffer and subtracted from the subsequent frame F i+i of the original video signal.
- the subscript "i" thereby denotes a time index.
- the cross-talk cancellation approach as outlined above tries to cancel the echo image regardless of whether the echo is actually visible in different parts of the image to be displayed.
- An improved method of pre-processing stereoscopic video data in order to avoid visible echo images in the images actually displayed takes into account the "visibility" of the echo image in different regions of an image frame to be displayed.
- Fig. 6 illustrates an ideal cross-talk compensation as aimed for by the examples of the present invention described herein. Accordingly, the luminance which is "lost" in the echo image is added to a current image frame. Additionally, the extra luminance stemming from the echo of the previous image frame is subtracted from the current image frame. That is, an echo image E i-1 is estimated from (e.g. left) image frame F i-1 ' as previously discussed above with respect to Fig. 5 . Another echo image E i is estimated from the succeeding (e.g. right) image frame F i . An echo compensated image frame F i ' is calculated by adding the current echo image E i and subtracting the previous echo E i-1 . In other words an echo compensated image frame F i ' is calculated by subtracting the difference echo image E i-1 -E i . This principle is illustrated in Figs. 7 and 8 .
- Figure 7 illustrates a sequence of frames F i-1 , F i , F i+1 of a video stream.
- frame F i-1 represents a left image
- frame F i represents a right image
- frame F i+1 again, represents a left image.
- the subscript "i" represents a time index or frame number.
- An echo image E i-1 is calculated from frame F i-1 ' (corrected in a previous step), whereby the echo image E i-1 represents the "ghost image" of the left image F i-1 ' appearing in the subsequent right image F i .
- the echo image E i-1 is used for "correcting" the subsequent frame F i a frame buffer is required for storing the image data.
- Another echo image E i is calculated from the frame F i , whereby the echo image E i represents the "ghost image” of the right image F i appearing in the subsequent left image F i+1 , or - in other words - the echo E i represents the luminance (or the image energy) which is "lost" in the right image F i .
- the corrected (i.e. echo compensated) frame F i ' is obtained by subtracting the echo difference E i-1 -E i from the current frame F i , or - in other words - the luminance resulting from the echo E i-1 of the preceding frame F i-1 is subtracted and the luminance "lost" due to the echo E i of the current frame F i is added.
- a high degree of echo extinction may be achieved resulting in a significantly improved stereoscopic image reproduction.
- the echo cancellation may be performed for each color channel (red, green, blue) separately, whereby the blue channel does not require a correction when using PDPs.
- a respective flow chart illustrates the echo cancellation in Fig. 8 . It should be noted that the steps of calculating the echo image (see box labelled "echo image” in Fig. 8a ) may be performed before or after the buffering of the frame. That is the boxes labelled "echo-image" and "frame buffer” may be interchanged in the example of Fig. 8a (this situation is illustrated in Fig. 8d ).
- Fig. 8a illustrates in an abstract manner a device for processing video data comprising a sequence of successive image frames F i-1 , F i , F i+1 .
- the device comprises a calculation unit 11 (labelled as 11a and 11b for the read and the green color channel, respectively) configured to receive an image frame F i from a video data source 10 and to calculate a first echo image E i based on the image frame F i .
- the device further comprises a further calculation unit 12 (12a and 12b) including a frame buffer 13 (13a, 13b) for providing a second echo image E i-1 calculated based on a further image frame F i-1 preceding the image frame F i (in the example of Fig.
- the echo image E i-1 is calculated using the compensated image frame F i-1 ' and is thus based on the image frame F i-1 ).
- An echo compensation unit 14 is configured to calculate an echo compensated image frame F i ' by subtracting the difference E i-1 -E i of the echo images E i-1 , E i from the image frame F i .
- the frame buffers 13a, 13b may be coupled upstream or downstream of the further calculation units 12a, 12b.
- the second echo image E i-1 is calculated from the compensated image frame F i-1 ' whereas the first echo image E i is calculated from the uncompensated image frame F i .
- both compensated or uncompensated image frames may be used for calculating estimations of the echo images E i , E i-1 .
- An alternative implementation is illustrated in Fig. 8b where both echo images are calculated directly from the current (uncompensated) image frame F i and the preceding (uncompensate) image frame F i-1 retrieved from a frame buffer.
- a third example is illustrated in Fig. 8c where, the echo image calculation units 11 and 12 are identical and the calculation has only be performed once.
- Fig. 8d which is essentially the identical to the example of Fig. 8 wherein the echo calculation and frame buffering is interchanged.
- Luminance i.e. energy
- luminance is added where the current frame is "loosing" energy without “polluting” the subsequent frame.
- the brightness of a frame may be subjected to a brightness modification function called "tilt function" which allows applying a small offset to low brightness levels only when required, so as to avoid negative brightness levels after compensation.
- the "tilt function” may include a non-linear component which allows to apply an offset to only these brightness levels where required without shifting black regions to gray.
- Exemplary tilt functions are illustrated in Figs. 9a-h which may be regarded as "modified gamma correction curves".
- Fig. 9 illustrates the effect of the brightness modification using the tilt function mentioned above.
- Fig. 9a illustrates a function that has no effect and corresponds to a gamma correction with a gamma value of unity. That is, in the example of Fig. 9a an unmodified gamma correction would be performed as it is common in display devices.
- Fig. 9b illustrates the effect of the tilt function which adds a higher offset to low brightness values than to high brigtness values. Thus the curve is "tilted” by adding the offset as compared to the linear function of Fig. 9a .
- Fig. 9c illustrates the case in which an additional non-linear tonality curve is included in the brightness modification.
- the goal of such a non-linear correction is to have a steeper growth of the luminance in dark gray areas while keeping the full black value at zero.
- a first gray level Go is selected that corresponds to the lowest gray level in the image that is not zero and where the non-linear transformation should start.
- a second gray level G 1 is selected that corresponds to the continuation of the linear region. The non-linear transformation will be applied between G 0 and G 1 only.
- the computation of the levels G 0 and G 1 and the parameterization of the transformation can be done automatically by analyzing a histogram of the ghost energy per level that cannot be compensated. That is, for each (low) gray level, it can be computed how many pixels exhibit a gray level for which cross-talk cannot be compensated (because negative brightness values would occur). Thus, a histogram of the non-compensable image regions is built. This histogram can be then used to compute the values of G 0 and G 1 and also to select among several non-linear functions. The transformation will be adapted to reduce as much as possible the peaks in the histogram.
- the actual value of OFFSET and the actual nonlinearity may be automatically adapted depending on the actual average brightness of the current frame. Thereby, the adaptation should not be performed too fast in order to avoid disturbing variances of the overall brightness of the image.
- the tilt function including the non-linear component may be combined with the actual gamma correction curve yielding a modified gamma correction curve.
- an automated adaptation of the offset may be used for the above-mentioned tilt function.
- a fixed tilt value i.e. the offset value OFFSET being a predefined value
- a fixed tilt value may deteriorate the contrast for all images for only improving a few images.
- An integrator evaluates on a per-frame-basis the total "ghost" energy which is the image energy that cannot be compensated, and, if a threshold value is exceeded, then tilt function is activated.
- tilt control More precisely, a "tilt control" algorithm is employed according to which two energy values are calculated and evaluated once per frame and using the tilt value of the previous frame:
- the "ghost energy” EG represents the luminous energy of the cross-talk present in that part of the image area where the effect of the echo image can not be compensated as the compensation would lead to a negative brightness value.
- the "tilt energy” ET represents the luminous energy of that part of the image area where the brightness level is below the “tilt value” OFFSET.
- each energy value EG, ET is compared with two threshold values:
- a decision to increase (inc), to decrease (dec) (by an increment or, respectively, decrement value STEP), or to keep the OFFSET value is taken using these thresholds A, B, C, D.
- An example is given on table below: EG > A A > EG > B B > EG ET > C dec OFFSET dec OFFSET dec OFFSET C > ET > D keep OFFSET keep OFFSET dec OFFSET D > ET inc OFFSET keep OFFSET dec OFFSET dec OFFSET
- the above table illustrates how the tilt value OFFSET of the subsequent frame may be computed based on the estimation of the values EG and ET computed from a current frame.
- the increment/decrement value STEP 1, so that the maximum change of the tilt value OFFSET per frame is 1.
- the threshold values have to be fine-tuned so as to match with the display device used, depending on its resolution, the amount of cross-talk, etc. These are rather empiric values resulting from tests and experimental optimization for each display type.
- the OFFSET value may be important to increase or decrease the OFFSET value by only a small amount (e.g. lower or equal 1) so as to avoid a "flashing" or “pumping" of the image.
- the additive cross-talk (energy added to the next image) is usually the most critical effect which is stronger than the energy “missing” (as it is “lost” in the subsequent frame).
- the "missing" energy LCDs are slow in both directions, i.e. increasing or decreasing luminance
- the additive cross-talk can be equally critical as (or even worse than) the additive cross-talk.
- the principle of using an adaptive tilt function should also be effective for the brightest (i.e. the light gray and white) regions of the image.
- An echo image effect may also be uncompensable when the value to be subtracted E i-1 -E i is negative and thus the correction would yield brightness values higher than the maximum available value. For instance, if a local brightness value is 1023 in 10 bit, no energy can be added for the respective pixel and the negative crosstalk cannot be compensated in this pixel position.
- This transformation can be combined with the previous tilt function (see Fig. 9b ) or with the combination of tilt and non-linear transformation ( Fig. 9c ).
- a similar concept to automate this correction can be applied as for the above-explained auto-tilt.
- the value ATTENUATION can be regarded as "tilt value” which is automatically adapted in a similar way as the "tilt value” OFFSET value as explained above. Accordingly, a ghost energy (i.e.
- the energy representing the luminous energy of an image resulting from cross-talk whose compensation would result in brightness values higher than a maximum brightness) is calculated as well as a a tilt energy (i.e. the energy difference between the maximum possible luminous energy and the actual luminous energy of that part of the image having a brightness higher than a pre-defined brightness threshold).
- a tilt energy i.e. the energy difference between the maximum possible luminous energy and the actual luminous energy of that part of the image having a brightness higher than a pre-defined brightness threshold.
- the ghost energy and the tilt energy are compared with one or more energy thresholds, and, dependent on the result of this comparison, the attenuation value ATTENUATION is increased, decreased or kept unchanged.
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Testing, Inspecting, Measuring Of Stereoscopic Televisions And Televisions (AREA)
Abstract
Description
- The present Invention generally relates to display devices for reproducing stereoscopic video data, in particular to display devices employing a field-sequential method and including an image cross-talk cancellation capability for improving the quality of three-dimensional image reproduction.
- The 3D perception from the Human Visual System (HVS) is based on the close side-by-side positioning of the eyes as shown in
Fig. 1 . Each eye takes a view of the same area from a slightly different angle. These two separate images are sent to the brain for processing. When the two images arrive simultaneously in the back of the brain, they are united into one picture. The human mind combines the two images by matching up the similarities and adding the small differences to catch finally a three-dimensional stereo picture. With stereovision, the HVS sees an object as solid in three spatial dimensions (width, height and depth) and it is the additional perception of the depth dimension that makes stereovision so rich and special. Moreover, a stereo picture will increase the impression of sharpness in the brain. - 3D images are generated using two video cameras positioned side-by-side in a similar way than the human eyes. Other methods mainly based on complex software are also able to generate artificial stereo pictures by ray tracing (simulation of light propagation). In the further discussion, these images will be referred to as left and right images. If right and left images stemming from a video source are displayed in a sequential and alternating manner as shown in
Fig. 2 and if a synchronized shutter system in front of the eyes allows the right image to only enter the right eye and conversely, then a three-dimensional video reproduction can be observed. The shutter can be mounted in eyeglasses and is synchronized with a display in which two constituent pictures are presented in alternation instead of simultaneously. The glasses occlude either the left eye or the right eye in synchronism with the image displaying. - A simple method to implement a stereoscopic display is based on the separation of sub-fields into left (L) and right (R) groups which are synchronized with the open and close stage of the LCD shutter glasses. An advantage of such a method is the compatibility of the flat panel display (FPD) between 2D and 3D modes. This compatibility is ensured through a simple change of the display mode (single or double frame rate).
- This method is often called "field-sequential" or "active-glass system" and enables to keep the full resolution of the display in 3D. Indeed, in case of polarizer systems (i.e. a passive glass system), each odd and even line is dedicated to another eye, thus reducing the displayed resolution in 3D by a factor two. Moreover, such polarizer filters are built on the front glass of the panel, thus reducing partly its brightness both in 2D as well as in 3D. Nevertheless, this field-sequential method can introduce other discomfort such as the introduction of time parallax between the two images, or the possibility of "ghosting" or crosstalk between the images due to the time response of the display (e.g. phosphor persistence in case of plasma display panels (PDPs) or grey-to-grey switching time in case of liquid crystal displays (LCDs). Most glasses-shutter systems use LCDs which work with polarized light. Currently, glasses using LCDs can provide good switching speed and reasonable extinction of the alternative lenses. The electro-optical polarizing shutters available on the market today transmit less than 30% of the unpolarized input light (rather than 50% for perfect polarizers) and this reduces the image brightness tremendously. Some eyeglass shutters are connected by wires to the monitor, others are controlled by infrared or by radio communication and are wireless.
- Displaying stereo pictures on a flat panel display also requires the capability to display two different pictures per frame (i.e. doubling the frame rate) which is a new challenge for this technology.
- The main problem encountered with such a solution is the problem resulting from the so-called "display response time" (also called "phosphor lag" in case of PDPs). As already mentioned, in the case of LCDs this problem is due to the slow response time of the liquid crystal when switching from a grey level to another grey level. In the case of PDPs, the phosphor elements associated with the colours red and green require too much time to switch off, and so a "shadow image" of the right image is still visible when displaying the left image and vice versa, which deteriorates the resulting stereoscopic image reproduction. This effect is often named "crosstalk" whereas this refers to the cause (i.e. incomplete separation of left and right images) or "ghost-image", which refers to the subjective perception of the images.
-
Figure 3 illustrates the response of each phosphor element to the same excitation in the case of a plasma display panel (PDP). The response time of the phosphor elements associated with the colors red and green is longer than that of the phosphor elements associated with the color blue, which is almost equal to the primary excitation (UV light caused by the gas or plasma discharge inside the PDP cells). These long reaction times for red and green materials exceed usually the reaction time of the viewing glasses when closing and will be therefore perceived by the "wrong" eye. - For the further discussion, the assumption shall be made that the displaying of a stereoscopic image starts with the left image. An image, which is seen by the right eye (respectively left eye), will be called a right image (respectively left image).
- As a result of the slowness of the red and green phosphor elements, the phosphor elements activated for the left image are still luminous while the right image is displayed or, in other words, after the opening of the right glass. Consequently, there will be a so-called "ghost image" (also denoted as "echo") visible in the right image but stemming from the left image, and on a subsequent left image an echo image stemming from the right image can be observed. This cross-talk effect is illustrated in
Figure 4 , which shows how subfields behave in such a configuration. - In addition to that, the energy lagging into the subsequent image (dedicated for the other eye) is energy that is missing for the correct eye. It can be seen from
Figure 3 that the areas enclosed by the three curves for red, green and blue (i.e. the integral) are similar but, if the shutter glasses would have been closed in synchronism with the blue phosphor, a part of the energy from red and green materials will be lost. - However, the stereoscopic system as described above requires the left image to be seen only by the left eye, and the right image to be seen only by the right eye. However, due to the slow decay of the luminance of the green and red phosphor elements when shutting off, the right eye will receive some fraction of the luminance of the left image and conversely. The phosphor lag will prevent a proper stereoscopic effect since the right eye receives both right and left information. The echo (or crosstalk) image is usually perceived as a kind of doubled image (remaining parts of left image are superimposed to the right one and vice versa) and lead to a lack of sharpness or even to a temporal loss of the depth perception in some particular cases (e.g. in case of images with strong contrast).
- The mentioned ghost images and the related image crosstalk are a problem that has to be considered when using a display technology with not-instant reaction time (such as PDPs and LCDs in field-sequential mode) for stereoscopic image reproduction. However, image cross-talk may also appear when using other video reproduction devices such as video projectors or the like, and the problems mentioned above are not limited to PDPs.
- Also some attempts have been made to alleviate the problem described above by preprocessing the video data before actually displaying the data, there is still a need for a device capable of high-quality stereoscopic image reproduction by particularly avoiding image cross-talk.
- A method for processing video data comprising a sequence of successive image frames is disclosed. In accordance with one example of the invention the method comprises: receiving an image frame from a video data source; calculating a first echo image based on the image frame; providing a second echo image based on a further image frame preceding the image frame; calculating an echo compensated image frame by subtracting the difference of the echo images from the image frame.
- The invention can be better understood referring to the following drawings and descriptions. In the figures like reference numerals designate corresponding parts. In the drawings:
- Fig. 1
- is a diagram illustrating the principle of ste-reoscopic vision;
- Fig. 2
- is a diagram illustrating the principle of ste-reoscopic image reproduction using time or field-sequential method;
- Fig. 3
- is a timing diagram illustrating the time re-sponse of different phosphor elements of a PDP;
- Fig. 4
- illustrates the effect of the phosphor lag when reproducing stereoscopic images using a PDP;
- Fig. 5
- illustrates by means of a flow diagram one method of cross-talk cancellation by subtracting the un-desired echo images;
- Fig. 6
- illustrates by means of a timing diagram the ef-fect of image cross-talk and an optimum compensa-tion thereof;
- Fig. 7
- illustrates the image cross-talk compensation ac-cording to one example of the present invention;
- Fig. 8
- illustrates different examples of
Fig. 7 by means of a flow diagram; and - Fig. 9
- illustrates different examples of brightness ma-nipulation before cross-talk cancellation.
- One option to avoid the image cross-talk as discussed in the introduction is to subtract an estimated echo image (or "ghost image"), which is obtained from one (e.g. left) image, from the subsequent (e.g. right) image. However, such an approach has some considerable drawbacks as does not allow for a full compensation of the echo image without deteriorating the quality of the resulting stereoscopic image. In particular a sufficient compensation of the echo image (i.e. a sufficient cross-talk cancellation) can only be achieved when the contrast of the image is reduced. Such a method is illustrated in
Fig. 5 . Thereby, the subtraction is done regardless of the cross-talk visibility. In other words, in regions without disparity (right image = left image), subtraction will be performed even though no disturbing effect is created in these regions. This will induce an undesired global loss of brightness. - The flow diagram of
Fig. 5 illustrates one exemplary method of pre-processing stereoscopic video data in order to avoid visible echo images in the images actually displayed. Accordingly, an echo image Ei is estimated from one frame Fi' of a video signal to be displayed. Thereby a frame represents the brightness values of the (red, blue and green) pixels composing one single left or right image. This echo estimation may be performed separately for each color channel, whereby in applications using PDPs for 3D image presentation the blue channel may remain uncompensated. Further a look-up table (LUT) of pre-calculated data may be used for such estimation. The estimated echo image Ei is stored in a frame buffer and subtracted from the subsequent frame Fi+i of the original video signal. In other words, one (e.g. left) frame Fi' of a video signal to be displayed is obtained from the corresponding (left) frame Fi of the original video signal by subtracting therefrom an echo image Ei-1, which is estimated from the preceding (e.g. right) frame Fi-1' (Fi'=Fi-Ei-1). The subscript "i" thereby denotes a time index. - Although resulting in an improved stereoscopic image presentation, the method outlined above with respect to
Fig. 5 does not achieve a full cancellation of the cross-talk induced by echo images. As a frame can only include positive brightness values, a full echo compensation can not be achieved in parts of an image that has low brightness values and where the subtraction mentioned above (Fi'=Fi-Ei-1) would yield negative values. In order to circumvent this problem an offset brightness may be added to the frame. As a result, however, regions originally appearing black or almost black will then appear as grey. - The cross-talk cancellation approach as outlined above tries to cancel the echo image regardless of whether the echo is actually visible in different parts of the image to be displayed. An improved method of pre-processing stereoscopic video data in order to avoid visible echo images in the images actually displayed takes into account the "visibility" of the echo image in different regions of an image frame to be displayed.
-
Fig. 6 illustrates an ideal cross-talk compensation as aimed for by the examples of the present invention described herein. Accordingly, the luminance which is "lost" in the echo image is added to a current image frame. Additionally, the extra luminance stemming from the echo of the previous image frame is subtracted from the current image frame. That is, an echo image Ei-1 is estimated from (e.g. left) image frame Fi-1' as previously discussed above with respect toFig. 5 . Another echo image Ei is estimated from the succeeding (e.g. right) image frame Fi. An echo compensated image frame Fi' is calculated by adding the current echo image Ei and subtracting the previous echo Ei-1. In other words an echo compensated image frame Fi' is calculated by subtracting the difference echo image Ei-1-Ei. This principle is illustrated inFigs. 7 and8 . -
Figure 7 illustrates a sequence of frames Fi-1, Fi, Fi+1 of a video stream. For the further discussion it may be assumed that frame Fi-1 represents a left image, frame Fi represents a right image and frame Fi+1, again, represents a left image. The subscript "i" represents a time index or frame number. An echo image Ei-1 is calculated from frame Fi-1' (corrected in a previous step), whereby the echo image Ei-1 represents the "ghost image" of the left image Fi-1' appearing in the subsequent right image Fi. As the echo image Ei-1 is used for "correcting" the subsequent frame Fi a frame buffer is required for storing the image data. Another echo image Ei is calculated from the frame Fi, whereby the echo image Ei represents the "ghost image" of the right image Fi appearing in the subsequent left image Fi+1, or - in other words - the echo Ei represents the luminance (or the image energy) which is "lost" in the right image Fi. The corrected (i.e. echo compensated) frame Fi' is obtained by subtracting the echo difference Ei-1-Ei from the current frame Fi, or - in other words - the luminance resulting from the echo Ei-1 of the preceding frame Fi-1 is subtracted and the luminance "lost" due to the echo Ei of the current frame Fi is added. Following this approach for echo cancellation a high degree of echo extinction may be achieved resulting in a significantly improved stereoscopic image reproduction. The echo cancellation may be performed for each color channel (red, green, blue) separately, whereby the blue channel does not require a correction when using PDPs. A respective flow chart illustrates the echo cancellation inFig. 8 . It should be noted that the steps of calculating the echo image (see box labelled "echo image" inFig. 8a ) may be performed before or after the buffering of the frame. That is the boxes labelled "echo-image" and "frame buffer" may be interchanged in the example ofFig. 8a (this situation is illustrated inFig. 8d ). - Generally
Fig. 8a illustrates in an abstract manner a device for processing video data comprising a sequence of successive image frames Fi-1, Fi, Fi+1. The device comprises a calculation unit 11 (labelled as 11a and 11b for the read and the green color channel, respectively) configured to receive an image frame Fi from avideo data source 10 and to calculate a first echo image Ei based on the image frame Fi. The device further comprises a further calculation unit 12 (12a and 12b) including a frame buffer 13 (13a, 13b) for providing a second echo image Ei-1 calculated based on a further image frame Fi-1 preceding the image frame Fi (in the example ofFig. 8a the echo image Ei-1 is calculated using the compensated image frame Fi-1' and is thus based on the image frame Fi-1). An echo compensation unit 14 is configured to calculate an echo compensated image frame Fi' by subtracting the difference Ei-1-Ei of the echo images Ei-1, Ei from the image frame Fi. Theframe buffers further calculation units - In the present example of
Fig. 8a , the second echo image Ei-1 is calculated from the compensated image frame Fi-1' whereas the first echo image Ei is calculated from the uncompensated image frame Fi. However, this is not necessarily the case, both compensated or uncompensated image frames may be used for calculating estimations of the echo images Ei, Ei-1. An alternative implementation is illustrated inFig. 8b where both echo images are calculated directly from the current (uncompensated) image frame Fi and the preceding (uncompensate) image frame Fi-1 retrieved from a frame buffer. A third example is illustrated inFig. 8c where, the echoimage calculation units 11 and 12 are identical and the calculation has only be performed once. A forth example is illustrated inFig. 8d which is essentially the identical to the example ofFig. 8 wherein the echo calculation and frame buffering is interchanged. - Using the above discussed novel approach for image cross-talk cancellation the echo compensation is adapted to the image content. Luminance (i.e. energy) is subtracted where "polluting" cross-talk stemming from the preceding frame superposes with the current frame, and luminance is added where the current frame is "loosing" energy without "polluting" the subsequent frame. This improves the overall quality of cross-talk cancellation, in particular at low brightness levels at which other methods experience difficulties in achieving a proper echo compensation. The novel method presented herein does not reduce image brightness of the overall image, thus increasing the margin for echo compensation in regions of low brightness levels as compared to standard approaches.
- The problem that a compensation is not possible in image regions where the subtraction would result in negative brightness values still remains. However, using the novel cross-talk cancellation approach as discussed above the actual impact on image quality due to this effect is significantly reduced. As explained with respect of
Fig. 5 negative brightness values may be avoided by adding a brightness offset (prior to echo compensation) which, however, results in black colour appearing gray. This is caused, for instance, when the value to be subtracted Ei-1-Ei is higher than the value of the current frame Fi. - In order to alleviate this effect the brightness of a frame may be subjected to a brightness modification function called "tilt function" which allows applying a small offset to low brightness levels only when required, so as to avoid negative brightness levels after compensation. Additionally, the "tilt function" may include a non-linear component which allows to apply an offset to only these brightness levels where required without shifting black regions to gray. In essence the application of such "tilt function" has a similar effect than a gamma correction. Exemplary tilt functions are illustrated in
Figs. 9a-h which may be regarded as "modified gamma correction curves". -
Fig. 9 illustrates the effect of the brightness modification using the tilt function mentioned above.Fig. 9a illustrates a function that has no effect and corresponds to a gamma correction with a gamma value of unity. That is, in the example ofFig. 9a an unmodified gamma correction would be performed as it is common in display devices.Fig. 9b illustrates the effect of the tilt function which adds a higher offset to low brightness values than to high brigtness values. Thus the curve is "tilted" by adding the offset as compared to the linear function ofFig. 9a . In an exemplary case of a brightness resolution of 10 bits (ranges from 0 to 1023) the tilt function may be written as OUT = IN + OFFSET · ((1023-IN)/1024), whereby IN is the input brightness (ranging from 0 to 1023), OUT is the output brightness and OFFSET the offset added to a brightness of zero.Fig. 9c illustrates the case in which an additional non-linear tonality curve is included in the brightness modification. The goal of such a non-linear correction is to have a steeper growth of the luminance in dark gray areas while keeping the full black value at zero. To perform that transformation, a first gray level Go is selected that corresponds to the lowest gray level in the image that is not zero and where the non-linear transformation should start. Then a second gray level G1 is selected that corresponds to the continuation of the linear region. The non-linear transformation will be applied between G0 and G1 only. - The computation of the levels G0 and G1 and the parameterization of the transformation can be done automatically by analyzing a histogram of the ghost energy per level that cannot be compensated. That is, for each (low) gray level, it can be computed how many pixels exhibit a gray level for which cross-talk cannot be compensated (because negative brightness values would occur). Thus, a histogram of the non-compensable image regions is built. This histogram can be then used to compute the values of G0 and G1 and also to select among several non-linear functions. The transformation will be adapted to reduce as much as possible the peaks in the histogram. An example for the non-linear transformation may be as follows: OUT = Go + SQRT(IN-G0)/SQRT(G1-G0) · (G1-G0). This is only an example given to better understand the concept. However, usually, more complex transformation may be applied using a LUT (look up table) in order to get better asymptotic behavior and smoother transitions between linear and non-linear parts of the transformation.
- The actual value of OFFSET and the actual nonlinearity (see
Fig. 9c ) may be automatically adapted depending on the actual average brightness of the current frame. Thereby, the adaptation should not be performed too fast in order to avoid disturbing variances of the overall brightness of the image. The tilt function including the non-linear component may be combined with the actual gamma correction curve yielding a modified gamma correction curve. - In accordance with a further embodiment of the present invention an automated adaptation of the offset may be used for the above-mentioned tilt function. A fixed tilt value (i.e. the offset value OFFSET being a predefined value) introduces - when permanently active - a significant decrease in the picture contrast for all images, regardless of whether these images are deteriorated by crosstalk in black area ("negative compensation") or not. This is undesired as 3D cross-talk is perceived by a human viewer only in a few extreme regions of an image. In other words, a fixed tilt value may deteriorate the contrast for all images for only improving a few images. To improve this situation the use of an "auto tilt" function is suggested where the tilt is only applied when it is necessary. An integrator evaluates on a per-frame-basis the total "ghost" energy which is the image energy that cannot be compensated, and, if a threshold value is exceeded, then tilt function is activated.
- More precisely, a "tilt control" algorithm is employed according to which two energy values are calculated and evaluated once per frame and using the tilt value of the previous frame:
- EG: Ghost Energy: The ghost energy represents the luminous energy of the cross-talk present in the image area which would have a negative brightness value if full compensation would be applied (which actually can not be done in realty). In other words, the "ghost energy" is the uncompensable energy of an echo image.
- ET: Tilt Energy: The tilt energy represents the luminous energy of the image area which has a brightness value lower than the "tilt value" OFFSET.
- That is, the "ghost energy" EG represents the luminous energy of the cross-talk present in that part of the image area where the effect of the echo image can not be compensated as the compensation would lead to a negative brightness value. The "tilt energy" ET represents the luminous energy of that part of the image area where the brightness level is below the "tilt value" OFFSET. These areas would therefore be strongly affected by this offset. Thus, there is a conflict of objectives between "compensating echo image effects" and "not brightening dark image regions".
- An important task is to find a good compromise between those objectives, as the dark image regions, which would be compensated when applying the tilt function, as well as the dark regions where no crosstalk is visible both become brighter due to the application of the tilt function. In other words, if an image contains a lot of (nearly) black image regions (e.g. a night scene with moon) and if only a very small area with cross-talk is appearing (cross-talk around the moon in a black sky), it would be better to use a very a low tilt value OFFSET (or a tilt value of zero) so as to avoid brightening the night scene. More generally, if an image has a huge amount of black (or dark gray), it is preferable not to use an OFFSET value to keep the contrast high, as the contrast impression is an important parameter relevant for the quality of the visual perception. Accepting a small cross-talk would have a lower impact on the 3D image than fully compensating the cross-talk but brightening the image. Therefore, each energy value EG, ET is compared with two threshold values:
- "ghost energy" EG is compared with an upper threshold A and a lower threshold B;
- "tilt energy" ET is compared with an upper threshold C and a lower threshold D.
- Subsequently, on a per-frame-basis a decision to increase (inc), to decrease (dec) (by an increment or, respectively, decrement value STEP), or to keep the OFFSET value is taken using these thresholds A, B, C, D. An example is given on table below:
EG > A A > EG > B B > EG ET > C dec OFFSET dec OFFSET dec OFFSET C > ET > D keep OFFSET keep OFFSET dec OFFSET D > ET inc OFFSET keep OFFSET dec OFFSET - The above table illustrates how the tilt value OFFSET of the subsequent frame may be computed based on the estimation of the values EG and ET computed from a current frame. In a first approach the increment/decrement value STEP = 1, so that the maximum change of the tilt value OFFSET per frame is 1. However to have smoother changes and a slower regulation speed, it may be useful to use lower values (e.g. STEP=0.1 means a change of 1 every 10 frames).
- The threshold values have to be fine-tuned so as to match with the display device used, depending on its resolution, the amount of cross-talk, etc. These are rather empiric values resulting from tests and experimental optimization for each display type.
- Following this concept it may be important to increase or decrease the OFFSET value by only a small amount (e.g. lower or equal 1) so as to avoid a "flashing" or "pumping" of the image.
- In case of PDPs, the additive cross-talk (energy added to the next image) is usually the most critical effect which is stronger than the energy "missing" (as it is "lost" in the subsequent frame). However, when using other display technologies such as LCDs, the "missing" energy (LCDs are slow in both directions, i.e. increasing or decreasing luminance) can be equally critical as (or even worse than) the additive cross-talk.
- In the latter case, the principle of using an adaptive tilt function should also be effective for the brightest (i.e. the light gray and white) regions of the image. An echo image effect may also be uncompensable when the value to be subtracted Ei-1-Ei is negative and thus the correction would yield brightness values higher than the maximum available value. For instance, if a local brightness value is 1023 in 10 bit, no energy can be added for the respective pixel and the negative crosstalk cannot be compensated in this pixel position.
- Therefore a similar "tilt function" may be used having the form OUT = IN - ATTENUATION · (IN/1024) as illustrated in
Figure 9d, 9e or 9g . This transformation can be combined with the previous tilt function (seeFig. 9b ) or with the combination of tilt and non-linear transformation (Fig. 9c ). Moreover, a similar concept to automate this correction can be applied as for the above-explained auto-tilt. In this case the value ATTENUATION can be regarded as "tilt value" which is automatically adapted in a similar way as the "tilt value" OFFSET value as explained above. Accordingly, a ghost energy (i.e. the energy representing the luminous energy of an image resulting from cross-talk whose compensation would result in brightness values higher than a maximum brightness) is calculated as well as a a tilt energy (i.e. the energy difference between the maximum possible luminous energy and the actual luminous energy of that part of the image having a brightness higher than a pre-defined brightness threshold). For each image frame, the ghost energy and the tilt energy are compared with one or more energy thresholds, and, dependent on the result of this comparison, the attenuation value ATTENUATION is increased, decreased or kept unchanged. The example explained further above with respect to the automatic adaptation of the "tilt" value OFFSET is - mutatis mutandis - also valid for the present example of automatic adaptation of the attenuation value ATTENUATION. In essence only the luminous energy scale is reversed. - Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
- Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods, and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
Claims (15)
- A method for processing video data comprising a sequence of successive image frames, the method comprises:receiving an image frame (Fi) from a video data source;providing a first echo image (Ei) based on the image frame (Fi);providing a second echo image (Ei-1) based on a further image frame (Fi-1) preceding the image frame (Fi);calculating an echo compensated image frame (Fi') by subtracting the difference (Ei-1-Ei) of the echo images (Ei-1, Ei) from the image frame (Fi).
- The method of claim 1 where providing the first echo image (Ei) and/or providing the second echo image (Ei-1) includes
either transforming an image frame (Fi) into the corresponding echo image
or transforming an echo compensated image frame (Fi-1') into the corresponding echo image (Ei-1). - The method of claim 2 where the transforming of an image frame (Fi) into an echo image includes applying a transformation function or a look-up table.
- The method of one of the claims 1 to 3 where, before the step of providing an echo compensated image frame (Fi') the image frame (Fi) is subject to a brightness modification function.
- The method of claim 4 where the brightness modification function includes a selective increase of low brightness values and/or a selective attenuation of high brightness values by respective offset or attenuation values (OFFSET, ATTENUATION).
- The method of one of the claims 1 to 5,
where the image frames are subject to a brightness modification function which is a linear function starting at an offset value (OFFSET), and/or
where the image frames are subject to a brightness modification function which is a linear function remaining an attenuation value (ATTENUATION) below a maximum brightness value. - The method of one of the claims 1 to 6,
where the image frames are subject to a brightness modification function which includes a non-linear transformation which may comprise a non-linear segment between two brightness values (G0, G1) and linear segments below the first brightness value (G0) and above the second brightness value (G1),
wherein the two brightness values are calculated based on the echo image. - The method of one of the claims 4 to 7 wherein the brightness modification function is adapted dependent on the brightness values of the current image frame.
- The method of one of the claims 4 to 8 wherein the offset and/or attenuation values are adapted depending on the brightness values of the current image frame.
- The method of one of the claims 1 to 9 wherein at least one echo image (Ei-1) is stored in a frame buffer.
- The method of one of the claims 1 to 10 wherein the image frames represent the brightness information of a red, a green or a blue colour channel.
- The method of one of the claims 8 or 9, including
calculating a ghost energy being the energy representing the luminous energy of an image resulting from cross-talk whose compensation would result in negative brightness values;
calculating a tilt energy being the energy representing the luminous energy of that part of the image having a brightness lower than a pre-defined brightness threshold;
comparing, for each image frame, the ghost energy and the tilt energy with one or more energy thresholds; and
increasing, decreasing, or keeping the offset value dependent on the result of the comparison. - The method of one of the claims 8, 9 or 12, including
calculating a ghost energy being the energy representing the luminous energy of an image resulting from cross-talk whose compensation would result in brightness values higher than a maximum brightness;
calculating a tilt energy being the energy difference between the maximum possible luminous energy and the actual luminous energy of that part of the image having a brightness higher than a pre-defined brightness threshold;
comparing, for each image frame, the ghost energy and the tilt energy with one or more energy thresholds; and
increasing, decreasing, or keeping the attenuation value dependent on the result of the comparison. - The method of claims 12 and 13, wherein ghost energy and tilt energy are compared with two different energy thresholds, respectively, so that the comparison is able to distinguish nine different cases.
- A device for processing video data comprising a sequence of successive image frames, the device comprises:a calculation unit (11) configured to receive an image frame (Fi) from a video data source (1) and to calculate a first echo image (Ei) based on the image frame (Fi);a frame buffer (13) for providing a second echo image (Ei-1) calculated based on a further image frame (Fi-1) preceding the image frame (Fi) using the calculation unit (11) or a further calculation unit (12);an echo compensation unit (14) configured to calculate an echo compensated image frame (Fi') by subtracting the difference (Ei-1-Ei) of the echo images (Ei-1, Ei) from the image frame (Fi).
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP11164807.7A EP2521358B1 (en) | 2011-05-04 | 2011-05-04 | Image Cross-talk Cancellation in Stereoscopic Video Display Devices |
PCT/EP2012/001897 WO2012150033A1 (en) | 2011-05-04 | 2012-05-03 | Image cross-talk cancellation in stereoscopic video display devices |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP11164807.7A EP2521358B1 (en) | 2011-05-04 | 2011-05-04 | Image Cross-talk Cancellation in Stereoscopic Video Display Devices |
Publications (2)
Publication Number | Publication Date |
---|---|
EP2521358A1 true EP2521358A1 (en) | 2012-11-07 |
EP2521358B1 EP2521358B1 (en) | 2016-09-14 |
Family
ID=46168391
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP11164807.7A Active EP2521358B1 (en) | 2011-05-04 | 2011-05-04 | Image Cross-talk Cancellation in Stereoscopic Video Display Devices |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP2521358B1 (en) |
WO (1) | WO2012150033A1 (en) |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2001258052A (en) * | 2000-03-14 | 2001-09-21 | Nippon Hoso Kyokai <Nhk> | Stereoscopic image display device |
EP1460857A1 (en) * | 2003-03-17 | 2004-09-22 | Deutsche Thomson-Brandt Gmbh | Method and device for compensating ghost images in time sequential stereoscopic images |
US20100271464A1 (en) * | 2009-04-22 | 2010-10-28 | Samsung Electronics Co., Ltd. | Apparatus and method for processing image |
WO2010150519A1 (en) * | 2009-06-24 | 2010-12-29 | パナソニック株式会社 | Image signal processing apparatus, image display apparatus, and image signal processing method |
-
2011
- 2011-05-04 EP EP11164807.7A patent/EP2521358B1/en active Active
-
2012
- 2012-05-03 WO PCT/EP2012/001897 patent/WO2012150033A1/en active Application Filing
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2001258052A (en) * | 2000-03-14 | 2001-09-21 | Nippon Hoso Kyokai <Nhk> | Stereoscopic image display device |
EP1460857A1 (en) * | 2003-03-17 | 2004-09-22 | Deutsche Thomson-Brandt Gmbh | Method and device for compensating ghost images in time sequential stereoscopic images |
US20100271464A1 (en) * | 2009-04-22 | 2010-10-28 | Samsung Electronics Co., Ltd. | Apparatus and method for processing image |
WO2010150519A1 (en) * | 2009-06-24 | 2010-12-29 | パナソニック株式会社 | Image signal processing apparatus, image display apparatus, and image signal processing method |
Also Published As
Publication number | Publication date |
---|---|
WO2012150033A1 (en) | 2012-11-08 |
EP2521358B1 (en) | 2016-09-14 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP5062674B2 (en) | System, method, and computer program product for compensating for crosstalk when displaying stereo content | |
US9571823B2 (en) | Image display apparatus and method | |
US9355455B2 (en) | Image data processing method and stereoscopic image display using the same | |
US8482605B2 (en) | Image processing device, image display device, and image processing and display method and program | |
EP2501139A2 (en) | Ghost-compensation for improved stereoscopic projection | |
US8941725B2 (en) | Method of processing three-dimensional stereoscopic image data and display apparatus for performing the same | |
EP2276267A2 (en) | Image signal processing apparatus and image display | |
GB2480363A (en) | Stereoscopic image display with reduced ghosting | |
EP2579241A1 (en) | Liquid crystal display device | |
KR101966335B1 (en) | Method for displaying an image in three dimensions on a display system and display system for displaying an image in three dimensions | |
US8896674B2 (en) | Video signal processing apparatus and video signal processing method | |
EP2456220B1 (en) | Three dimensional image display device | |
US20120274749A1 (en) | Stereoscopic video display device | |
US20110316974A1 (en) | Method and system for reducing ghost images of three-dimensional images | |
JP2012145656A (en) | Stereoscopic image display device and control method therefor | |
JP2001054143A (en) | Crosstalk reduction method and system in stereoscopic image display by time division system | |
EP1460857A1 (en) | Method and device for compensating ghost images in time sequential stereoscopic images | |
EP2521358B1 (en) | Image Cross-talk Cancellation in Stereoscopic Video Display Devices | |
EP2521359B1 (en) | Image cross-talk cancellation in stereoscopic video display devices | |
JP2013077863A (en) | Stereoscopic display device and stereoscopic display method | |
WO2013082176A2 (en) | Apparatus, method and article for generating a three dimensional effect including using inverted images and/or passive filters | |
JP4138451B2 (en) | Display apparatus and method | |
US8786598B2 (en) | Pixel-intensity modulation technique for frame-sequential stereo-3D displays | |
CN102868902B (en) | Three-dimensional image display device and method thereof | |
KR101398451B1 (en) | Display apparatus |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR |
|
AX | Request for extension of the european patent |
Extension state: BA ME |
|
RIN1 | Information on inventor provided before grant (corrected) |
Inventor name: CORREA, CARLOS Inventor name: LUEBCKE, GEROLD Inventor name: WEITBRUCH, SEBASTIEN |
|
17P | Request for examination filed |
Effective date: 20130507 |
|
RBV | Designated contracting states (corrected) |
Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR |
|
17Q | First examination report despatched |
Effective date: 20130620 |
|
APBK | Appeal reference recorded |
Free format text: ORIGINAL CODE: EPIDOSNREFNE |
|
APBN | Date of receipt of notice of appeal recorded |
Free format text: ORIGINAL CODE: EPIDOSNNOA2E |
|
APBR | Date of receipt of statement of grounds of appeal recorded |
Free format text: ORIGINAL CODE: EPIDOSNNOA3E |
|
APBV | Interlocutory revision of appeal recorded |
Free format text: ORIGINAL CODE: EPIDOSNIRAPE |
|
GRAP | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOSNIGR1 |
|
INTG | Intention to grant announced |
Effective date: 20160503 |
|
GRAS | Grant fee paid |
Free format text: ORIGINAL CODE: EPIDOSNIGR3 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR |
|
REG | Reference to a national code |
Ref country code: GB Ref legal event code: FG4D |
|
REG | Reference to a national code |
Ref country code: CH Ref legal event code: EP |
|
REG | Reference to a national code |
Ref country code: IE Ref legal event code: FG4D |
|
REG | Reference to a national code |
Ref country code: AT Ref legal event code: REF Ref document number: 830117 Country of ref document: AT Kind code of ref document: T Effective date: 20161015 |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R096 Ref document number: 602011030292 Country of ref document: DE |
|
REG | Reference to a national code |
Ref country code: LT Ref legal event code: MG4D |
|
REG | Reference to a national code |
Ref country code: NL Ref legal event code: MP Effective date: 20160914 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: NO Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20161214 Ref country code: RS Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 Ref country code: FI Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 Ref country code: LT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 Ref country code: HR Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 |
|
REG | Reference to a national code |
Ref country code: AT Ref legal event code: MK05 Ref document number: 830117 Country of ref document: AT Kind code of ref document: T Effective date: 20160914 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: LV Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 Ref country code: NL Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 Ref country code: GR Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20161215 Ref country code: SE Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: RO Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 Ref country code: EE Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: PLFP Year of fee payment: 7 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: PT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20170116 Ref country code: SK Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 Ref country code: BE Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 Ref country code: IS Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20170114 Ref country code: ES Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 Ref country code: SM Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 Ref country code: BG Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20161214 Ref country code: AT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 Ref country code: PL Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 Ref country code: CZ Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R097 Ref document number: 602011030292 Country of ref document: DE |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: IT Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 |
|
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DK Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 |
|
26N | No opposition filed |
Effective date: 20170615 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: LU Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20170531 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: SI Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 |
|
REG | Reference to a national code |
Ref country code: CH Ref legal event code: PL |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: MC Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 |
|
REG | Reference to a national code |
Ref country code: IE Ref legal event code: MM4A |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: LI Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20170531 Ref country code: CH Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20170531 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: LU Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20170504 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: IE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20170504 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: PLFP Year of fee payment: 8 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: MT Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20170504 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: AL Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: HU Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT; INVALID AB INITIO Effective date: 20110504 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: CY Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20160914 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: MK Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: TR Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 20160914 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 20230517 Year of fee payment: 13 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: GB Payment date: 20240522 Year of fee payment: 14 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: DE Payment date: 20240625 Year of fee payment: 14 |